clinical correlations

Clinical Correlations
A. Abnormal functions of organelles
1.Tay-Sachs disease* – occurs in Northeast European Jewish ancenstry
a.Cell component: Lysosome
b.Enzyme deficiency: hexosaminidase A.
c.Metabolic build-up: GM2-ganglioside
d.Clinical Consequence: Motor and mental impairment
2. Hurler’s disease
a.Cell component: Lysosome
b.Enzyme deficiency: Lack of lysosomal a-L-iduronidase
c.Metabolic build-up: Accumulation of dermtan sulfate in tissues
d.Clinical Consequence: Growth and mental retardation
3. Mitochondrial cytopathy
a.Cell component: Mitochondrion
b.Defect in oxidative phosphorilation.
c.Increase in # and size of muscle mitochondria
d.Clinical Consequence: High basal metabolism without hyperthyroidism
4.Kartagener’s syndrome*
a.Cell component: Microtuble
b.Deficiency: Lack of dynein in cilia and flagella.
c.Lack of arms of the doublet microtubules
d.Clinical Consequence: Immotile cilia and flagella with male sterility and chronic respiratory infection (also can cause problems in female fertility with ectopic pregnancy – per Dr. Crissman)
5. Proinsulin Diabetes
a.Cell component: Secretory granule
b.Defect of proinsuling cleaving enzyme
c.Clinical Consequence: High blood proinsulin content (diabetes)
6. I-Cell disease
a.Cell component: Golgi complex
b.Enzyme deficiency: Phosphotranferase
c.Metabolic build-up: Inclusion-particle storage in fibroblasts
d.Clinical Consequence: Psychomotor retardation, bone abnormalities
B. Abnormal functions of the cells.
1.Vacuolization is a common response to physiologic and pathologic stimuli.
2.Storage of metabolites occurs during metabolic disorders
a.Lysosomal storage disease
b.Glycogen storage disease
c.Lipid storage
d.Storage of pigmented materials
C. pH problems
#
Metabolic and Respiratory acidosis and alkylosis
D.**Phenylketonuria** - phenylalanine
E. Actin filaments, Intermediate filaments, Microtubules

1. Anemia and
2. Hereditary Spherocytosis
   1. Spectrin is an Actin filament (microfilaments) associated protein that helps bind actin and maintain flexibility (to get through the capillaries for example)
   2. Located in the cortical networks
   3. Defects in the cytoskeletal components of erythrocytes result in various conditions marked by abnormally shaped cells.
   4. HS is caused by synthesis of an abnormal spectrin that exhibits defective binding to band 4.1 protein (anchoring protein).
   5. RBCs of patients with this conditiona are more fragile and transport less oxygen compared with normal erthrocytes.
   6. These spherocytes are preferentially destroyed in the spleen, leading to Anemia.
3. Muscular dystrophy
   1. Dystrophin is an Acitn filament associated protein located in the muscle cortical networks
4. Action of Drugs on actin filaments
   1. Cytochalasins A,B,C,D, & E

i.Secrected by various fungi
ii.Molecules bind to the end of actin filaments and prevent further polymerization

1. Phalloidin

i.Components from the mushroom Amanita phalloids
ii.Binds to actin filaments and stabilizes them against depolymerization
iii.Strong poison – function of the cell is stopped.

1. Action of Tubulin binding drugs (microtubules)
   1. Because cancer cells divide much more rapidly than normal cells, cancers are more susceptible to being poisoned by mitotic inhibitors such as colchicine, paclitaxel, and the Vinca alkaloids.
   2. Colchicine, Colcemid

i.Inhibit the addition of tubulin molecules to microtubules
ii.Leading to microtubule depolymerization

1. Vinblastine, Vincristine

i. Induce the formation of paracrystaline aggregates of tubulin
ii. See Cell Cycle

1. Taxol

i.Stabilizes – so cannot disassemble

F. Defects in membrane proteins
1. Acquired Hemolytic Anemia “Paroxysmal Nocturnal Hemoglobinuria (PNH)”
a. Acquired means it happens in the stem cells not in the germline
b. Glycosylphosphatidylinositol (GPI) anchor
i. PIGA enzyme is essential for GPI synthesis
ii. Mutation in PIGA enzyme causes loss of GPI anchor
iii. GPI is needed for membrane localization of some proteins
iv. Proteins such as CD 59 cannot act effectively when not anchored
c. Cells with this defect are more sensitive to complement-mediated lysis, leading to thrombosis
2. Cancer:
a. Alterations of membrane protein and/or lipid are key to metastasis and invasion of tumor cells as they spread throughout the body.
b. A specific type of membrane transporter protein (called MDR, multi drug resistance) is the basis for the development of multidrug resistance that can occur during chemotherapy.(see active transport)
3. Diabetes:
a. Defective insulin signaling, defective function of glucose transporters
b. Defects in GLUT-4 (facilitated diffusion) can lead to insulin resistance and Type II diabetes
c. Also see “abnormal function of cells” , proinsulin diabetes –disease involves improper cleavage of insulin
4. Heart Disease:
a. Defective cell-cell communication (example – connexins in arrhythmias, will be discussed by other instructors)
5. Membrane proteins are useful drug targets – control signal in and out of cells


Losec Gastric H+/K+ ATPase
Prozac Na+ - coupled serotonin transporter
Ouabain Na+/K+ ATPase (heart)


6. Hereditary sperocytosis (see actin filaments for additional info)

G. Protein folding disorders
1. Creutzfeldt-Jakob disease (CJD)
a. Prions =
1. Transmissible spongiform encephalopathies [TSEs]; fatal neurodegenerative disorders affecting humans and other mammals
2. Normal prion proteins are a-helical & soluble, prion diseases are due to aggregates of insoluble prion b-sheets
b. Human
1. Creutzfeldt-Jakob disease (CJD) diagnosed in ~1 per million per yr
c. Scrapie (sheep)
d. Bovine spongiform encephalopathy (BSE) (cow)
e. Chronic wasting disease (CWD) (mule deer, elk)
f. CJD has 3 main classifications:
1. Sporadic CJD = 85% (no known source)
2. Inherited (fCJD) = 10-15% (genetic mutation in coding sequence for prion protein)
3. Infectious: iatrogenic (iCJD) = < 5% horizontally transmitted by medical or surgical, human material injected, etc
4. variant (vCJD) = BSE --> CJD??? (1996 first reported case in UK)
2. Alzheimers
3. Parkinsons
4. Amyotrophic lateral sclerosis (ALS), sometimes called Lou Gehrig's disease
5. Huntingtons
6. Cystic fibrosis *not discussed
7. Gauchers *not discussed
H. Post translational protein modification
1.Scurvy- caused by vitamin C deficiency
a.Hydroxyl group addition to proline and lysine stabilizes fibers of collagen
b.Proline residues (certain ones) of collegen need to be hydroxylated
c.Ascorbate (vitamin C) is an essential co-factor of prolyl hydroxylase
d.Collegen synthesized in the absence of Ascorbate have a lower Tm
e.Fibers formed from the abnormal collegen contribute to
1.Skin lesions and
2.Blood vessel fragility in scurvy
I. Disorders, BLOOD
1. Red Blood cells
a. Hereditary sperocytosis (see actin filaments for additional info)
b. Anemia (see actin filaments for additional info)
c. PNH (see membrane proteins for additional info)
2.White blood cells
a.HIV
1.HIV attacks helper T cells (CD4) and destroys them.
2.The B and Cytotoxic T cells are not being aided in activation by cytokines
b.Phemphigus vulgaris
1.Autoimmune disease
2.Antibodies to the cadherin desmoglein
3.The desmosomes are destroyed particularly in epidermis
4.The pts loose skin integrity
3.Hemophilia
a.blood clotting disorder
b.Plasma needed to determine ability to clot
4.Glanzmann’s disease – blood clotting disorder, see cell motility
J. Connective tissue disorders
1.Hypercellular obesity (hyperplastic obesity)
a.Increased # of fat cells (white adipose cells)
b.Usually due to overfeeding as infant
c.More serious of the 2 conditions
d.Harder to treat
2.Hypertrophic obesity
a.Increase in size of fat cells(white adipose cells) i.e. more lipid
b.Same # of cells as before
c.More common
3.Anaphylactic shock
a.Mast cells (fixed cells of connective tissue) are involved in inflammatory response
b.Upon antigen exposure, substances such as heparin and histamine are released
c.If too much is released, pt can go into shock
1.fluid is leaking out of the blood vessels into connective tissue
2.loss of blood volume
3.constricting of smooth muscles of the bronchials
4.Scurvy (see Postranslational modifications)
5.Ehlers-Danlos VII
a.Due to to procollagen peptidase change
b.Hyperflexible joints, dislocations, soft skin
6.Emphysema
a.Lung dysfunction caused by breakdown of elastic fibers
b.Pts often barrel chested
7.Marfan’s Syndrome
a.Caused by poor microfibril formation in elastic fiber
b.Tendency to rupture aorta, and other blood vessels
8.Hyaluronic acid
a.Creates a physical barrier against bacteria
b.Bacteria use hyaluronidase to get by this barrier
9.Edema, Pitting
a.Abnormal build of interstitial fluid in the extra cellular matrix
b.Causes:
1.Blocked (or removal of) lymphatics
a)surgery (i.e. radical mastectomy)
b)elephantiasis
c)Tsetse fly (African trypanosomiasis)
2.Blocked venus return
a)Compromised veins i.e. pregnancy
3. Liver disease
a)Insufficient albumin (produced by Liver) to pull water back in vessel
4.Increased vascular permeability
a)Histamine from mast cells
b)Asthma
c)Anaphylactic shock
5. Hypertension
a) Due to increased hydrostatic pressure at arterial end of capillary bed
b) Diuretics remove water from arterial system
6.Starvation
a)Causes lack of plasma proteins that results in water remaining in the extracellular matrix
10.Myxedema – non-pitting edema
a.Due to over production of GAG’s during hypothyroidism
b.Doesn’t pit – called “Mucous Edema”
K. Vitamins and Vitamin deficiencies
1.Vitamin C
a.Scurvey – Vitamin C deficiency
b. See Postranslational modifications
2.Thiamine (B1)
a.Thiamine is a coenzyme for the decarboxylation of a-keto acids such as pyruvic acid and a-keto glutaric acid
b.Deficiencies in B1 can lead to
1.disturbances in carbohydrate metabolic activity and decreased transketolase activity, particularly in erythrocytes and leukocytes
2.clinically, cardiovascular and neurologic lesions, as well as emotional disturbance
3.Such problems can occur in the hospital when i.v. glucose is given with no B1
c.Transketolase - Red cell transketolase activity is reduced in deficiency of thiamine (vitamin B1), and may be used in the diagnosis of Wernicke's encephalopathy and other B1-deficiency syndromes if the diagnosis is in doubt.[1] Apart from the baseline enzyme activity (which may be normal even in deficiency states), acceleration of enzyme activity after the addition of thiamine pyrophosphate may be diagnostic of thiamine deficiency (0-15% normal, 15-25% deficiency, >25% severe deficiency).[2]
d.Other diagnostic tests for deficiency
1.Measurement of the ratio of lactic to pyruvic acid in blood after administration of glucose
2.blood and urinary pyruvic acid levels are characteristically elevated
e.“Dry” Beri Beri
1.Caused from a chronic dietary Thiamine (B1)deficiency
2.symptoms include:
a)peripheral neuropathy
b)fatigue
c)impared capacity to work
f.“Wet” Beri Beri
1.Developes from a severe Thiamine (B1)deficiency
2.Symptoms in addition to neurological manifestations
a)Cardiovascular symptoms more apparent including
(1)Heart enlargement
(2)tachycardia
b)Heart failure is common after stress
c)Edema
d)Anorexia
g.Wernicke-Korsakoff syndrome
1.chronic Thiamine (B1)deficiency
2.have a defective transketolase that exhibits a reduced affinity to TPP. (Thiamine pyrophosphate (TPP) is a coenzyme for pyruvate dehydrogenase, α-ketoglutarate dehydrogenase and transketolase. The first two of these enzymes function in the metabolism of carbohydrates, while transketolase functions in the pentose phosphate pathway to synthesize NADPH and the pentose sugars deoxyribose and ribose. TPP is synthesized by the enzyme thiamine pyrophosphokinase, which requires free thiamine, magnesium, and adenosine triphosphate.)
3.Seen in pts. w/ chronic alcoholism b/c poor nutrition coupled with impaired absorbtion of the vitamin
4.Symptoms include
a)Weakness or paralysis
b)Impaired mental function
3.Niacin (B3)
a.NAD+ is a derivative of Niacin
b.Pellegra
1.Cause by eficiency in Niacin
2.Symptoms include
a)Dermatitis
b)Diarrhea
c)Dementia
4.Riboflavin (B2)
a.Flavin adenine dinucleotide FAD
1.Coenzyme of most flavoproteins
2.Contains the vitamin riboflavin (B2)
b.Flavin mononucleotide FMN
1.Derivative of riboflavin (B2)
2.Important roll in Complex 1 of the Electron Transport chain
5.Pantothenic Acid
a.Contained in Coenzyme A
b.cannot be synthesised by humans
c.must be supplied in diet to ensure CoA formation
d.no known diseases due to deficiency


L. Electron transport and Oxydative phosphorylation

1. Ischemia

a.Due to tack of oxygen
b.In the cardiac muscle this can lead to:
1. Ischemic myocardium
2.Decreased ATP
3.Swelling
4.Leakage of enzymes
5.Cell necrosis (muscle)
6. Infarction (heart attack)
7.possible sudden death

1. Drugs and other compound that inhibit Electron transport chain:
   1. Rotenone, (and Sodium Amytal - barbiturate)

1.Between Complex I and Q

1. Antimycin A

1.between Cytb and Cyt c1 in Complex III
c.Cyanide and carbon monoxide
1.Complex IV
2.Cyanide blocks the cyta’s ability to bind with O2

1. Drugs and other compounds that uncouple oxidative posphorylation
   1. .2,4-Dinitrophenol – once a weight loss drug
   2. Dicumarol – anticoagulant
   3. Fatty acids in brown adipose tissue (to produce heat, i.e. hibernation)
   4. Uncoupling protein
   5. How does it act?

1.Increases the permeability of the mitochondrial membrane to H+ allowing them to return (or bringing them back) into the matrix without the formation of ATP i.e. no phosphorylation

1. What is its effect on i) respiration and ii) formation of ATP.

1.O2 consumption i.e. respiration increases
2.No ATP is produced

1. Distinguish between effects on O2 consumption on:
   1. inhibition of electron transport

1.Diminished O2 consumption because no electrons are coming down the chain that require oxygen

1. uncoupling of oxidative phosphorylation

1.Increased O2 consumption because oxygen is being used in the chain but no energy in the form ATP is being produced


M. Active transport
1. Congestive heart failure
a.Cardiotonic steroid drugs act on inhibiting the function of Na+/K+ ATPase (active transport)
1.Digitalis used to increase the strength of heart muscle contractions without increasing heart rate
2.It inhibits the Na+/K+ pump leading to an increase of sodium in the cell (3 sodiums out, 2 potasiums in)
3.this leads to an increase in Ca++ in the cell from a CA++ /Na+ transporter
4.Calcium-mediated signals act to increase contraction strength of the heart muscle
2. Multi-drug resistant tumors
a.Chemotherapy drugs are small and can diffuse across the membrane
b.ABC (ATP binding cassette) pump MDR1 recognize these drugs as toxic and pump them out
c.These pumps are amplified in some cancers
d.Liver expresses these pumps in normal tissue
3. Cystic fibrosis
a.Mutation (possible protein misfolding) in the Cystic Fibrosis Transmembrane Regulator (CFTR) causes it not to reach the apical surface
b.CFTR acts as a Chloride ion pump
c.Loss of this pump causes loss of water and sodium in the extracellular space
d.This leads to thick mucous à defective respiratory tract cilia and increased infections
N. Cell motility
1.Glanzmann’s disease
a.Platelets must bind with fibrinogen to form clot
1.platelets first bind to collagen or thrombin
2.this activates integrin on platelets to bind with fibrinogen
b.Lack of b3 integrin causes excessive bleeding due to lack of clotting
2.Cancer, metastisis
a.Phosphorylation of integrin inactivates it allowing cells to migrate
O. Cell cycle
1.Cancer, chromosome defects
a.Nondisjuction causes accumulation of chromosome defects
b.Either multiple copies, single copies or accumulation of partial
c.M-phase checkpoint (spindle attachment) responsible for catching these errors
2.Tumor formation
a.Loss (or mutation) of p53 protein occur in ½ of all cancers
1.Li-Froumeni syndrome – rare form of inherited cancer
2.P53 acts as a tumor suppressor by blocking cell cycle progression or promoting apoptosis
b.Rb protein acts as a molecular switch that operates the restriction point
1.Restriction point prevents cells from entering S phase when conditions are unfavorable
2.Rb gene located on chromosome 13
3.Mutation may be inherited, and the 2nd copy lost by somatic mutation “Two Hit Hypothesis”
4.Retinoblastoma – tumor of the eye found exclusively in young children
3.Chemotherapy
a.Alkaloids
1.Vincristine and Vinblastine
2.Block spindle formation
3.used to treat Wilm’s tumor and cancers of the lung, breast and testes
4.see also “Actin filaments…”
b.Antitumor antibiotics
1. Doxorubicin and Mitomycin-C
2.Block S phase
3.used to treat testicular cancer and leukemia
c.Antimetabolites
1.6-mercaptopurine and 5-fluorouracil
2.bock cell growth by interfering with S phase
3.tumors of the gastrointestinal tract, breast and ovary
d.Cdk inhibitors
1.flavopiridol, roscovitine – in clinical testing
2.block progression of cell cycle by inhibiting Cdk’s